The message of Ephesians 5:22-33: "The picture doesn't save; the person does."
Marriage - and sexual expression which forms a "one flesh" union - is described as a "picture" of Christ's faithful love for His people.
Though marriage and sexuality are good gifts - they are not ultimate. They do not save.
Jesus - the person - saves.
The gospel is good news because everything we'd be tempted to look for in romance, marriage, and sexual expression - pleasure, intimacy, companionship, exhilaration, wholeness - is found in our union with Christ to a far more perfect degree.